Think about it: If the standard render buffer between view stages would change its size for every stage, you had to reallocate it many times per frame in a view chain with different stage sizes. You would not be happy with the frame rate.

The standard render buffer has a fixed size, only determined by the largest stage in all your chains. This is why you observe that it grows when the view resolution grows, but it never shrinks. If you need a stage buffer of a smaller size, just use an individual buffer for that stage, as you already did with the camera view buffer.